In Situ Recovery Method for Cation-Contaminated PEM Fuel Cells Using CO ₂

Cationic contaminants in the membrane electrode assembly (MEA) of a proton-exchange membrane (PEM) fuel cell result in substantial, generally considered irreversible performance losses. Here, we show a novel in situ method to remove cationic contaminants from an MEA by high-current density operation of the cell with a CO ₂ –O ₂ cathode feed under wet-cold conditions (i.e., at high relative humidity and low temperature). In this process, CO ₂ dissociates to protons and bicarbonate anions in the aqueous phase in the cathode electrode, whereby the thus-formed protons ion-exchange with the metal cations in the electrode’s ionomer phase; the metal cations in the aqueous phase are then removed via the exhaust water. Utilizing cobalt ion doped model MEAs with carbon-supported platinum catalysts (Pt/C), this method is validated via 5 cm ² active area single-cell measurements, using various CO ₂ –O ₂ cathode feeds. For optimized operating conditions, ∼92% of the Co ²⁺ cations can be removed within 4 h. In presence of Ce ³⁺ as radical scavenger, Co ²⁺ cations can be removed with high selectivity. When applied to MEAs with a Pt _2.5 Co/C based cathode, their H ₂ /air performance before and after extended voltage cycling drastically improves, showcasing that this method can improve the durability of Pt-alloy-based MEAs.